Because the Chinese language uses thousands of characters--in contrast to the English language's use of 26 characters--the development of modern Chinese word processing equipment is a substantial problem. Obviously, a typewriter keyboard consisting of thousands of keys is impractical.
Phonetic (sometimes called phonemic) input schemes, based on the use of normal keyboards, are often used to input Chinese character text into a computer or word processor. These schemes known as the Mandarin Phonetic system in Taiwan and the Hanyu Pinyin system in the People's Republic of China involve the transliteration, for example, of the five following Chinese characters:
respectively into the five following single syllables reflecting the pronunciation of the Chinese characters: EQU tai2 wan1 you3 tai2 feng1
Because this phonemic input does not require special keyboards or the mastery of special coding schemes, its use is advantageous. However, since the number of pronounced Chinese syllables is significantly fewer than the number of Chinese characters, it suffers from the problem of ambiguity. A well-educated Chinese may be expected to know about 6000 characters, but the number of syllables is about 1200. Thus, one syllable may represent many different characters. For example, in the Hanyu Pinyin transliteration system, all the following characters are pronounced shi4:
Not surprisingly, translation of the 5-syllable phrase EQU tai2 wan1 you3 tai2 feng1
into Chinese characters presents over 21,000 (i.e., 9.times.5.times.6.times.9.times.9) different combinations of characters since "tai2", "wan1", "you 3", "tai2", and "feng1" respectively represent at least 9,5,6,9, and 9 different Chinese characters.
As described in their paper ("Removing the Ambiguity of Phonetic Chinese by the Relaxation Technique,"Computer Processing of Chinese & Oriental Languages Vol. 3, No. 1, May 1987) Lin and Tsai, attempting to overcome the above-described ambiguity problem, propose a method of converting phonetic Chinese syllables to character Chinese using the relaxation process widely used in image analysis problems, such as edge detection, curve detection and shape recognition. More specifically, they employ the relaxation process to obtain the optimal path through the lattice of possible characters, making use of the lexical probabilities of the characters given the syllables and the transition probabilities of adjacent characters and adjacent syllables.